The present invention relates to power steering apparatuses including an electric motor for generating an assist steering effort.
Japanese Patent Application Publication No. 2002-211425 discloses a power steering apparatus with an electric motor, in which a temperature sensor is provided at a motor drive section of a control unit. The temperature of the electric motor is estimated by: assuming an initial temperature of the electric motor to be equal to a temperature value detected by the temperature sensor when an ignition switch is turned on; computing an estimated temperature increase on the basis of a value of a motor current supplied to the electric motor; and adding the estimated temperature increase to the initial temperature. When the temperature sensor is judged as failed, then the motor current is limited to a motor current value with which both of the control unit and the electric motor can continuously operate without being overheated.